Process and apparatus for grinding piston and other rings



June 12, 1956 J. M. HALDEMAN 2,749,672

PROCESS AND APPARATUS FOR GRINDING PISTON AND OTHER RINGS Filed April10, 195] 4 Sheets-Sheet 1 y 5 Zmnentor WW attorneys June 12, i956 J. M.HALDEMAN 2,749,672

PROCESS AND APPARATUS FOR GRINDING PISTON AND OTHER RINGS Filed April10, 1951 4 Shaets-Sneet 2 ZSnventor g l fii/zzkwwz Bu I [g a E 2;

(Ittornegs June 12, 1956 J. M. HALDEMAN 2,749,672

PROCESS AND APPARATUS FOR GRINDING PISTON AND OTHER RINGS Filed April10, 1951 4 Sheets-Sneet 3 3nvcutor attorney June 12, 1956 J. M. HALDEMANPROCESS AND APPARATUS FOR GRINDING PISTON AND OTHER RINGS Filed April10, 1951 4 Sheets-Sheet 4 fizz/725942222; W j attongq hrl PROCESS ANDAPPARATUS FOR GRINDING PISTON AND- OTHER RINGS John M. Haldeman,Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich, acorporation of Delaware Application April 10, 1951, Serial No. 220,167

21 Claims. (Cl. 51-103) This invention relates to a process andapparatus for producing resilient packing rings.

The principal object of the invention is to provide a simple process forforming split resilient packing rings and the provision of simpleapparatus for carrying out certain steps in this process whereby thesurfaces of the resilient ring, so formed, uniformly engage surfaces of.relatively movable members in sealing engagement.

The steps in the process and apparatus by which this object isaccomplished will be clearly understood by reference to the followingdetailed description and drawings illustrating this process andapparatus for carrying out this process.

Figure 1 illustrates the form of the steel ring material and the ring inthe preliminary steps in the process.

Figure 2 is a schematic view of the apparatus for carrying out one stepof the process with parts of the apparatus and rings shown broken awayand in section.

Figure 3 is a schematic view of apparatus employed in another step ofthe process with parts shown broken away.

Figure 4 is a schematic view of apparatus for accomplishing anadditional step in the process with the ring shown broken away and insection.

Figure 5 is a schematic view of one form of apparatus for carrying. outanother step in the apparatus with parts of the apparatus and the ringsshown broken away and in section.

Figure 6 is a plan view of another form of apparatus with parts shownbroken away and in section, for carrying out the step of the processaccomplished by the apparatus shown in Figure 5.

Figure 7 is an end elevation View taken on line 77 of Figure 6 withparts shown broken away and in section.

Figure 8 is an enlarged sectional view taken on line 8-8 of Figure 7with parts shown broken away and in section.

Figure 9 is a view similar to Figure 8 with certain parts of modifiedform and other parts shown broken away and in section.

Figure 10 is a view similar to Figure 7 of a modification of theapparatus shown in Figure 7.

Figure 11 is a View similar to Figure 8 of the modified apparatus shownin Figure 10.

Figure 12 is an enlarged perspective view of a detail shown in Figures10 and 11.

As best seen in Figure la, resilient rings are formed of round steelwire which is rolled to a rectangular section, as shown in Figure 1b,and wound in the form of a helix, see Figure 10, after which each coilof the helix is cut to provide circular split rings 1, see Figure 1d,with helical side surfaces and uniform radial thickness.

The rings 1, in the form shown in Figure 1d, are next deflected intooval form with the sides flat and heat treated to retain the rings inthis form by the apparatus shown in Figure 2. This apparatus comprises aframe including a base 3 having a vertical mandrel 5 of oval crosssection provided with a base flange 7 with a flat nited States Patent2,749,672 Patented June 12, 1956 upper face 8. The mandrel flange 7 issecured to the central portion of the base 3 of the frame. A pluralityof upstanding lugs 9 are secured to the base 3 of the frame inconcentric relation to the vertical center line of the mandrel 5. Eachof the lugs 9 is provided with a clamp screw 11 threaded radiallytherethrough, with respect to the mandrel center line. The inner end ofeach screw 11 engages a separate, vertically disposed clamp bar 13. Aclamping plate 15 is attached by a clamp screw 17 threaded vertically inthe upper end of the mandrel 5 on the vertical center line thereof andthe clamping plate 15 provided with an annular flange 19 on the lowerface concentric to the vertical axis of the mandrel and having aninternal diameter slightly larger than the major diameter of the ovalmandrel 5 and a flat lower face. A plurality of split rings 1 in theform shown in Figure 1d are placed on the mandrel 5 with the ring gapsin vertical alignment, as shown in the dotted lines in Figure 2, alongone side of the oval mandrel 5. The radius of curvature of the mandrelsurface at a point immediately opposite the ring gaps is maximum and theradius of curvature of the mandrel decreases progressively from thispoint toward each end of the ring. The clamp screw 17 extending throughthe clamp plate 15 is then tightened to draw the annular flange 19 ofthe clamp plate downwardly onto the stacked rings 1 to thereby retainthe sides flat and parallel with the flat, lower end surface of theflange 19 of the clamp plate and the upper flat surface 8 of the mandrelflange 7, as best shown in Figure 2. The clamp screws 11 are thentightened to deflect the inner surfaces of the rings 1 into uniformengagement with the oval surface of the mandrel 5. In order to insureuniform engagement of the inner peripheral surfaces of the rings 1 onthe mandrel 5 the clamp screw 11 adjacent the point of maximum radius ofcurvature of the mandrel surface is tightened first and other clampscrews 11 either side of this point and toward the ring gaps aresuccessively tightened. With the ring clamped in the frame 3 in thisform, the frame is placed in a heat treating furnace 21 and heated forsuflicient time at proper temperature to cause the rings to remain inthe form in which they are clamped in the frame.

The rings are made and sprung round in the manner described so that whenthey are placed in piston ring grooves and contracted within an enginecylinder the outward radial pressure applied by the rings on theinterior surface of the cylinder will be relatively uniform throughoutthe peripheral length of each ring. A more complete explanation of howthe rings are made in this form and the apparatus for heat treating therings to relieve the internal stresses thereof which result from bendingthe rings into the desired form is disclosed by Haldeman application S.N. 228,207, filed in the United States Patent Ofiice May 25, 1951. Therings are sprung round during the grinding operation herein disclosed sothat the expansion of the rings against the grinding wheel employed willfinish the rings so that they will apply substantially uniform pressureto the inner surface of the engine cylinder throughout the peripherallength of each ring.

After the rings 1 cool, the sides of each ring are ground flat betweentwo flat rotating grinding wheels 23 and 25, as shown schematically inFigure 3, in a well known manner.

The next step of the process consists in abrading the outer peripheralsurface of the oval split rings 1 while held in contracted circular formby means of apparatus shown in Figures 6 to 12 or by means of theapparatus shown in Figure 5.

The abrading apparatus as best seen in Figures 6 to 12 generallycomprises a base plate 35 having a driving motor 37 mounted thereon andan upstanding plate 39, serving as a bearing member, is secured to thebase 35. As best seen in Figures 6, 7, 8 and 9, the bearing member 39 isprovided with a central opening having a bushing 41 therein and twelveopenings, of smaller diameter, arranged in a circle around the axis ofthe central opening. Each of these smaller diameter openings has abushing 43 therein, as best shown in Figure 8.

The driving motor is provided with a driving shaft 45 having a pinion 47thereon, shown in Figure 6, in mesh with a gear 49 keyed on the adjacentend of a driven shaft 51, as best illustrated in Figure 8. A spacingcollar 53 is located on the shaft 51 between the gear 49 and anothergear 55, also keyed to the shaft 51. A thrust washer 57 is placed on theshaft between the gear 55 and the larger diameter bearing portion of theshaft 51, which bearing portion is rotatably supported in the bushing 41in the central opening of the bearing member 39. Another thrust washer59 is placed on the opposite end of the bearing portion of the shaftbetween the bearing member 39 and a shaft flange 61 adjacent the otherend of the shaft 51. The flange 61 is provided with a reduced diameterpilot flange portion 63 on the outer end and having a threaded axialopening in the outer end face. A nut 64 is threaded on the shaft 51adjacent the gear 49 and serves to retain the gears 49 and 55, collar 53and thrust washers 57 and 59 on the shaft 51 with the thrust washers inrunning engagement with opposite sides of the bearing member 39. Ringsupporting rollers, generally indicated by the reference character 65,are rotatably supported in each of the bushings 43 in the bearing member39. Each roller 65 is provided with a tapered end surface 67, acylindrical ring supporting and driving surface 69 adjacent thereto andprovided with an enlarged diameter ring guiding flange portion 71adjacent the supporting surface and a reduced diameter bearing portion73 and a small diameter opposite end portion 75, as best seen in Figures6, 7 and 8. The bearing portion 73 of each roller 65 is rotatablysupported in one of the bushings 43 in the bearing member 39. A pinion77 is secured by means of a machine screw 78 to the smaller diameter endportion 75 of each roller and each of these pinions 77 meshes with thegear 55. A thrust washer 79 is placed on the smaller diameter portion 75of each roller between the pinion 77 and the bearing member 39 to limitend play of each of the rollers 65. A circular ring retaining flange 81is provided with a reduced diameter end portion 83 forming a ringguiding flange 84 facing the guiding flanges 71 on the rollers 65. Theflange 81 is provided with an axial bore 85 and a pilot counter bore 87in the end face of the retaining flange within the guide flange 84. Aclamp screw 88 having a washer 89 thereon, provided with a radial slot90 for quick removal, is threaded into the axial opening in the outerend of the pilot flange portion 63 of the shaft 51, as best seen inFigures 7 and 8. After placing a split oval ring 1 on the reduceddiameter portion 83 of the retaining flange 81 and tightening the clampscrew 88 the external peripheral surface of the ring 1 may be engagedwithin the tapered ends 67 of the rollers 65 and compressed andcontracted into circular form while being moved axially inwardly intofrictional driving engagement with the cylindrical supporting anddriving surfaces 69 of the rollers 65. During this movement of the ring1 the counter bore 87 in the flange 81 is piloted on the pilot flangeportion 63 of the driving shaft 51 and the inner end face of the flange81 is clamped in driving engagement with the outer face of the flangeportion 61 of the shaft 51. The internal peripheral surface of the ring1, when the ring is supported and contracted into circular form betweenthe rollers 65, is disengaged from the reduced diameter portion 83 ofthe retaining flange 81 and the sides of the ring 1 are positionedbetween the guiding flanges 71 of the rollers 65 and the guiding flange84 of the retaining flange 81. The ring retaining flange 81, as bestshown in Figure 8, is provided with diametrically disposed, axiallyextending openings through which pilot pins 91 are inserted. The innerends of the pilot pins 91 are shown projecting into pilot grooves 93provided in the external peripheral surface of the flange portion 61 ofthe shaft 51 and these pins pilot the counter bore 87 in the retainingflange onto the pilot portion of the shaft 51 when the clamping screw 88is tightened. With the ring 1 contracted into circular drivingengagement with the rollers 65, when these rollers are driven by meansof the driving motor 37, shaft 51 and meshing gears and pinions, thecircular contracted ring 1 is rotated about the axis of the shaft 51.

Grinding of the external peripheral surface of the ring 1 to a truecylindrical surface is accomplished by a grinding wheel 95, shown indotted lines in Figures 7 and 8, and rotatable about an axis at rightangles to and in the center plane of the ring 1. The grinding wheel 95is shown in Figure 7, positioned in a slot 97 provided in the bearingmember 39, extending radially with respect to the shaft 51 between apair of rollers 65, and in abrading engagement with the outer peripheralsurface of rotating ring 1. A gear cover 99 encloses the pinions andgears and is removably secured to the base 35 and bearing member 39.

The grinding wheel 95 is preferably rotated in the direction of thearrow shown in Figure 8 which urges the ring 1 into engagement with theoutwardly facing end surfaces of the flanges 71 of the rollers 65. Therotating grinding wheel 95 is moved slowly into the slot 97 until thewheel just engages and grinds off any high spots in the external surfaceof the compressed ring 1, resulting from unequal stresses therein. Whenthese high spots are removed the grinding wheel is fed inwardly a slightamount further, just suflicient to grind the external peripheral ringsurface to a true circle after which the wheel is moved out of grindingcontact with the ring and the ring is removed. This machine providescircularly disposed driving and supporting rollers to rotate and toretain an oval split ring in circular form with the sides parallel andto grind the outer peripheral surface-to a true circular form in whichit is to be used whereby the outer peripheral surface of the ring andthe flat sides are in uniform sealing engagement with the wall of acylinder and the sides of a piston ring groove. In that the grindingwheel 95, which, as previously explained, is mounted for rotation aboutan axis at right angles to the ring 1 and in the vertical center planethereof, a slightly concave cylindrical external surface is formed inthe ring by the grinding wheel. The machine described above is modifiedslightly as shown in Figures 10, l1 and 12 to permit rotation of thegrinding wheel 95 about an axis located in the vertical center plane ofthe ring and to thereby grind a true cylindrical, external peripheralsurface on the contracted ring. As best seen in Figures 10 and 11 thisapparatus differs from that described above by locating the axis of thegrinding wheel 95 above and in the vertical center plane of the ring 1and substituting stationary ring guiding members, indicated generally bythe reference characters 101 and 103, in place of the two rollers 65located on opposite sides of the grinding wheel slot 97 shown in Figure7 in the bearing member 39 and by supporting the other rollers 65 inneedle bearing 105 and the shaft '51 in a needle bearing 107, as shownin Figure 11. As best seen in Figure 12, each of the guiding members 101and 103 is provided with a cylindrical projection 109 on one side of amounting flange 111 and a ring guiding projection 113 on the other sidethereof. Each of these cylindrical projections 109 is inserted in one ofthe two topmost openings in the bearing member 39 in place of a pair ofrollers and machine screws are shown in Figure 10 extending throughthese openings in the mounting flanges 111 and are threaded intothreaded openings in the bearing member 39 on opposite sides of thevertical grinding wheel slot 97. This positions the guide projections113 in the plane of and above the ring 1, and on opposite sides of theslot 97. Arcuate ring guiding surfaces 115 and 117 are provided in theunder sides. of the ring guiding projections 113, which arcuate surfacescontact the ring 1 and are segments of a circle passing through thepoints contact of the rollers 65 with the contracted ring 1, as bestseen in Figure 11. The upper surfaces 121 and 123 of the guideprojections 113 are segments of a circle concentric with and of largerdiameter than the grinding wheel 95 to provide clearance therefor whenthe Wheel is lowered into grinding contact with the ring 1 between theseupper arcuate surfaces 121 and 123 of the ring guiding projections 113.The guiding projections 113 are preferably made of hard material, as thecontracted ring 1 is slidable on the arcuate under surfaces 115 and 117thereof during grinding of the ring 1, annd are subject to abrasiveparticles from the grinding wheel 95. A ring retaining flange 125, ofidentical form to the flange 89 shown in Figure 8, is provided and theflange 125 may,, if desired, be provided with identical openings forpilot pins 91, such as shown in Figure 8. The ring retaining flange 125is provided with a threaded opening located eccentrically in the outerface, and a pilot pin 127 is threaded therein and a plate 129 is pivotedon the pivot pin 127 and is provided with an arcuate slot 131 by whichthe plate is engaged by the clamping screw 88 threaded in the end of theshaft 51. As previously described, drawingup of the clamping screw 83moves the ring retaining flange 125 axially inward-1y into the adjacentpilot portion 63 of the shaft 51 and contracts the ring 1 intofrictional driving engagement with the rollers 65 and also causes thering to be slidably engaged with the guiding surfaces 115 and 117 of thering guiding members 101 and 103.

Grinding out the high spots of the ring 1 and forming a true cylindricalouter peripheral surface on the ring 1 is accomplished by slow downwardfeed of the grinding wheel 95 into contact with the rotating ring 1 inthe same manner as previously described.

The apparatus shown in Figure 9 differs from those previously describedand shown in Figures 6, 7, 8, 10, 11 and 12 by providing the ringdriving and supporting rollers 133 with an annular ring supportinggroove 135 therein. The oval split ring 1 is insertable into frictionaldriving engagement with the bottom of the roller grooves 135 by bendingthe ends of the split ring 1 into overlapping relation and letting thering spring back into contact with the bottom of the grooves 135 in therollers 133 in which grooves the ring is retained in circular form. Noring'retaining flange is necessary with this apparatus and the rollerdriving shaft 137 is accordingly not provided with a pilot portiontherefor. The roller driving shaft 137 is supported for rotation in abushing 41 and each of the rollers 133 are supported in bushings 43 inopenings in the bearing support member 39 in the same manner as thatshown in Figure 3. With the apparatus shown in Figure 9 the axis of thegrinding wheel is located at right angles to the vertical center planeof the ring in the manner described with reference to the apparatusshown in Figures 6, 7 and 8.

A true cylindrical surface may also be formed on a stack-up of ovalsplit rings 1 by means of the apparatus shown in Figure 5. Thisapparatus comprises a mandrel 139 having an external flange 141 adjacentone end. A stack of oval split rings 1 with the sides ground flat arestacked on the end of the mandrel 139 adjacent the mandrel flange and aclamping plate 143 is attached by means of a clamping screw 145 threadedin the outer end of the mandrel to retain the rings in contractedcircular form in axial compression between the ciarnping plate 143 andmandrel flange 141 after contraction of the rings by insertion of themandrel with the rings thereon into a suitable cylindrical jig, notshown. The mandrel 141 with the rings thereon is then insertable axiallyinto abrading relation with a plurality of elongated honing stones 147arranged in a circle and having internal cylindrical surfaces andsecured in a hollow, oscillatable and variable stroke head 149 of ahoning apparatus. The mandrel is held stationary within the honingstones and in axial alignment with the head 149. The mandrel clampingscrew 143 is then loosened to permit the rings 1 to expand intoengagement with the internal cylindrical surfaces of the honing stonesand then retightened. The head 149 is then oscillated and reciprocatedwith a long stroke to remove any high spots of the rings 1. Movement ofthe head 149 is then stopped and the clamping screw is loosened, topermit further expansion of the rings into tighter engagement with thestones, after which the head is then oscillated and reciprocated with ashort stroke with the rings loose on the mandrel. This causes the ringsto rotate slightly with respect to the mandrel and thereby causesgreater relative reciprocation of the stones past the rings to produce asmooth cylindrical surface to be formed on the external peripheralsurface of the rings. After grinding of the external surface of therings 1 by the apparatus including a grinding wheel, shown in Figures 6to 8, or either of the modifications thereof, one modification beingshown in Figures 18 to 12 and another being shown in Figure 9 or bymeans of the apparatus shown in Figure 5, including honing stones, theinner periphery of the rings are bored to a true cylindrical surface.This is done in any well known manner by compressing a plurality of therings in a cylindrical sleeve and boring the internal surface with therings by a boring tool axially movable with respect to the rings. Therings now have a uniform radial thickness.

After boring of the rings they are mounted in circular form on an arborand oil grooves are turned in the external peripheral surface and theouter edges of this surface are chamfered by means of forming tools 27,29, 31 and 33, shown schematically in Figure 4.

After the oil grooves have been turned in the external peripheralsurface and the edges of this surface are chamfered, the externalsurface is finished ground by means of any of the various modificationsof the apparatus described, including a grinding Wheel or by means ofthe apparatus including the honing stones.

The gaps in the ends of the rings are next finished by supporting therings in circular form in a hinged two-part cylindrical fixture and theend surfaces of the rings are milled off.

The rings are next supported in circular form in a mandrel serving ascathode electrode located in a plating bath and the outer peripheralsurfaces are plated with chromium or other metal.

The piated external peripheral surfaces of the rings are next abraded toform a smooth cylindrical surface thereon by means of any of the variousmodifications of the apparatus including a grinding wheel, or by meansof the apparatus including the honing stones.

Rings formed in the above described manner when positioned in the ringgrooves of a piston and slidable in a cylinder, exert uniform radialforce on the cylinder wall and the external peripheral surfaces of therings accordingly engage the cylinder wall in uniform, sliding, sealingengagement, and the sides of the ring are positioned in sealingengagement with the walls of the ring grooves in the piston.

I claim:

1. In a rotary supporting apparatus, a support member, rollers havingtapered end surfaces and external guide flanges intermediate the endsthereof and rotatably supported in a circle on said support member,driving means operatively connected to said rollers for rotating saidrollers, and engaging means having a guide flange adapted to be disposedin opposed relation to said roller guide flanges and being movableaxially with respect to said roller guide flanges.

2. In a rotary supporting apparatus, a support member, rollers rotatablymounted in a circle on said support member and having tapered endsurfaces and external guide flanges intermediate the ends thereof,driving means operatively connected to said rollers for rotating saidrollers, and circular engaging means disposed within and movable axiallywith respect to said tapered end surfaces.

3. The process of forming a true cylindrical surface on a splitresilient ring consisting of moving the ring into frictional drivingengagement with converging and parallel surfaces of rotary driving meansdisposed in a circle, and engaging the exterior peripheral surface ofthe rotating ring with rotary abrading means.

4. In a rotary supporting apparatus, a support, driving and supportingrollers rotatable in said support about individual axes disposed in acircle, said rollers having guiding flanges located in a plane normal tothe surfaces of said rollers and facing outwardly of the frame, a flangeaxially movable with respect to said guiding flanges and beingpositioned to extend within said guiding flanges and driving meansoperably connected to said rollers for rotation thereof.

5. In a rotary supporting apparatus, a support member, supporting meanson the support member and having cylindrical guiding surfaces disposedradially and equidistantly around a central axis, certain of saidsupporting means having external cylindrical guiding surfaces and beingrotatably mounted on the support member about axes parallel to thecentral axis, an adjacent pair of said supporting means beingnon-rotatably secured to the support means and having internalcylindrical guiding surfaces of segmental form, and driving meansoperatively connecting the rotatable supporting means for rotationthereof.

6. In a rotary supporting apparatus, a support member, a driving motor,a plurality of driving rollers rotatable on the support member aboutindividual axes parallel to and disposed in a circle about a centralaxis, each of said rollers having an annular flange located in a planenormal to the rollers, the rollers having tapered end portions taperingradially inwardly, engaging means having a flange movable axially withrespect to the tapered portions of the rollers and into a positionopposite and in spaced relation to said annular flange, and meansoperatively connecting the rollers to the driving motor for rotationthereby.

7. In a rotary supporting apparatus, a support member, a shaft rotatablysupported therein, a driving motor operably connected to the shaft,retaining flange piloted for axial movement on one end of the shaft,clamping means for moving the retaining flange axially in wardly intoendwise engagement with the shaft, a plurality of driving and supportingrollers rotatable on the support member above axes disposed in a circleabout the shaft, each roller having an external flange located in aplane normal to the rollers and facing toward the retaining flange andan end surface tapering radially inwardly adjacent the retaining flange,means operatively connecting the rollers with the shaft for rotationthereby and a pair of guide means secured to the support members betweenadjacent rollers, each of said guide members having an arcuate surfaceforming a segment of a circle having a radius equal to the radialdistance from the axis of the shaft to each of the rollers.

8. An apparatus for abrading split resilient rings which comprises ringcontracting means, means engaging the said ring across the outerperipheral surface thereof for supporting said ring in the formestablished by said contracting means, means for rotating saidsupporting means for driving said ring in rotation about the axis ofsaid ring by frictional engagement between the outer peripheral surfacesof said ring and said supporting means, and means rotatable on an axisat one side of said rotating means and in a plane parallel to saidsupporting means and intersecting said ring for abrading said surface ofsaid ring while said ring is so rotated, contracted and supported.

9. An apparatus for abrading split resilient rings which comprises ringcontracting means, a plurality of supporting means adapted to engagesaid ring around the outer peripheral surface thereof for supportingsaid ring in the form established by said contracting means, meansengaging a side surface of said ring for moving said ring from saidcontracting means to said supporting means, means for rotating saidsupporting means for frictionally driving said ring by resilientengagement between said outer peripheral surface of said ring and saidsupporting means, and means for abrading a surface of said ring while sorotated and contracted and supported.

10. An apparatus for abrading split resilient rings which comprises ringcontracting means, a plurality of rollers adapted to engage the outerperipheral surface of said ring for retaining said ring in the formestablished by said contracting means, means disposed at one side ofsaid rollers and adapted to engage a side surface of said ring andmovable toward said rollers along the axis of said ring for moving saidring axially through said contracting means and into said rollers, meansfor rotating said rollers for frictionally driving said ring in rotationabout the axis of said ring, and means for abrading said outerperipheral surface of said ring while said ring is so rotated andcontracted and supported.

11. An apparatus for abrading split resilient rings which comprises aplurality of rollers arranged about an axis for supporting a ring incontracted form, converging ring supporting means axially aligned withsaid rollers for contracting said ring to said form, means disposed atone side of said rollers and adapted to engage a side surface of saidring and movable toward said rollers along the axis of said ring formoving said ring axially through said contracting means and into saidrollers, diverging supporting means axially aligned with said rollersfor expanding said ring to original form upon the movement of said ringaxially away from said rollers, means for rotating said rollers forfrictionally driving said ring while said ring is supported therein andabout the axis of said ring, and means for abrading said ring while saidring is so supported and contracted and rotated within said rollers.

12. An apparatus for abrading split resilient rings which comprises aplurality of supporting rollers arranged in parallel relation to oneanother about an axis, ring contracting means disposed at one side ofsaid rollers for contracting said ring, means disposed at one side ofsaid rollers and adapted to engage a side surface of said ring andmovable toward said rollers along the axis of said ring for moving saidring axially through said contracting means and into said rollers, meansfor rotating said rollers while said ring is supported therein, andmeans for abrading said ring while said ring is so rotated, contractedand supported.

13. The process of forming a true surface on a split resilient ringwhich comprises applying radially directed forces to said ring toradially contract said ring to a predetermined size, applyingtangentially directed forces to the outer peripheral surface of saidring while so contracted to rotate said ring about the axis thereof, andabrading the outer peripheral surface of said ring during the rotationalmovement thereof about said axis.

14. The process of forming a true surface on a split resilient ringwhich comprises moving said ring axially while applying radiallydirected forces to said ring to radially contract said ring to apredetermined size, applying tangentially directed forces to the outerperipheral surface of said ring while so contracted to rotate said ringabout the axis thereof, and abrading the outer peripheral surface ofsaid ring during the rotational movement thereof about said axis.

15. The process of forming a true surface on a split resilient ringwhich comprises moving said ring axially while applying radiallydirected forces to said ring to radially contract said ring to apredetermined size, applying tangentially directed forces to the outerperipheral Surface of said ring while so contracted to rotate said ringabout the axis thereof, abrading the outer peripheral surface of saidring during the rotational movement thereof about said axis, and movingsaid ring axially while removing said radially directed forces toradially expand said ring to the original size thereof.

16. The process of forming a true surface on a split resilient ringwhich comprises applying radially directed forces to said ring tocontract said ring to a predetermined size, supporting the outerperipheral surface of said ring while so contracted on a plurality ofrollers having the axes thereof disposed substantially in parallelrelation to the axis of said ring, rotating said ring by rotating saidrollers about the axes thereof, and abrading the outer peripheralsurface of said ring while said ring is so rotated and contracted.

17. The process of forming a true surface on a split resilient ringwhich comprises applying radially directed forces to said ring tocontract said ring to a predetermined size, supporting the outerperipheral surface of said ring while so contracted on a plurality ofrollers having the axes thereof disposed substantially in parallelrelation to the axis of said ring, rotating said ring by rotating saidrollers about the axes thereof, and abrading the outer peripheralsurface of said ring between a pair of said rollers and while said ringis so rotated and contracted.

18. A process of forming a true surface on a split resilient ring whichcomprises applying radially directed forces to said ring to contractsaid ring to a predetermined size, supporting the outer peripheralsurface of said ring while so contracted on a plurality of rollershaving the axes thereof disposed substantially in parallel relation tothe axis of said ring, rotating said ring by rotating said rollers aboutthe axes thereof, supporting said ring between a pair of said rollers bysliding engagement with guide means adapted to be engaged by the outerperipheral surface of the ends of said ring when said ends tend toexpand between said pair of rollers during the rotation of said ring,and abrading the outer peripheral surface of said ring between said pairof rollers and said guide means and while said ring is so rotated andcontracted.

19. The process of forming a true surface on a split resilient ringwhich comprises radially contracting said ring until the outerperipheral surface thereof forms a circular cylindrical surface aboutthe central axis of said ring, rotating said ring about said centralaxis, and abrading said circular cylindrical surface of said ring .whilesaid ring is so rotated and contracted and by arcuate movement ofabrading means transversely of said surface and about an axis externallyof said ring and extending substantially transversely to said centralaxis.

20. An apparatus for abrading split resilient rings which comprises aplurality of rollers mounted on a support and having the axes thereofdisposed in parallel relation and having the inner surface elementsthereof arranged in a circular cylindrical orbit about a central axis,means for rotating said rollers about the axes thereof for rotating asplit resilient ring when said ring is contracted within said rollers toexpand the outer peripheral surface of said ring into frictional drivingengagement with said rollers, and means for abrading the outerperipheral surface of said ring, said abrading means being formed torotate in a plane intersecting said ring and ex tending between anadjacent pair of said rollers and rotating about an axis disposedoutwardly of said orbit and substantially normally to said axes and tosaid central axis.

21. An apparatus for abrading split resilient rings which comprises aplurality of rollers mounted on a sup port and having the axes thereofdisposed in parallel relation and having the inner surface elementsthereof arranged in a circular orbit about a central axis, means forrotating said rollers about the axes thereof for rotating a splitresilient ring when said ring is contracted within said rollers toexpand the outer peripheral surface of said ring into frictional drivingengagement with said rollers, means for abrading the outer peripheralsurface of said ring, said abrading means being formed to rotate in aplane intersecting said ring and extending between an adjacent pair ofsaid rollers and rotating about an axis disposed outwardly of said orbitand substantially normally to said axes and said central axis, and guidemeans between said adjacent pair of rollers and said abrading means andhaving arcuate circular cylindrical surfaces formed thereon about saidcentral axis and within said orbit and being adapted to engage the outerperipheral surface of said ring adjacent pair of said rollers.

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